Avalanche forecast

Swan Range

Flathead Avalanche Center
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Avalanche danger

Sat
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Out of date — this forecast expired 3 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Plan your day to avoid traveling on or under steep, sun-baked slopes. Warm temperatures and sunshine can make the snow surface slide easily. Rollerballs and pinwheels should steer you toward terrain that is shaded from the sun. You can trigger a slide in wind-drifted snow along ridges, saddles and gullies. 

Avalanche problems

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–2

    Yesterday (Thursday), warming and sunshine moistened surface snow enough to initiate Wet Loose avalanches. Increasing cloud cover in the afternoon limited the extent of warming and preserved dry snow on slopes that did not receive direct sunshine. Today, high pressure will continue to chip away at the snowpack. Natural and human-triggered avalanches are most likely on steep slopes that face the sun or near rock outcrops, which can soak up solar radiation and enhance warming in the surrounding snow. Large slopes can produce avalanches big enough to bury you. 

    Hone in on surface conditions as you travel today. Dry snow that becomes moist for the first time will develop this problem quickly. Slopes capped by a stout melt-freeze crust–or have already been worked over by Wet Loose activity– will be slower to transition. Moist surface snow can be identified by its capacity to form a snowball. Rollerballs and pinwheels indicate the snow surface is ready to slide and should steer you to slopes that tilt away from the sun. Plan your trip to avoid traveling on or under steep slopes that have been baking in the sun. 

    (1/8/2023)

    Small rollerballs due to the warming of the surface snow.

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2

    Snowfall and southwesterly winds during the first half of the week formed slabs of wind-drifted snow on upper-elevation, leeward slopes. Cam and I found touchy wind drifts and blowing snow in the Swan Lake area on Wednesday. Winds tapered to calm-light yesterday and today it should be more difficult–but not impossible–to trigger an avalanche in wind-drifted snow. 

    Look for pillows or dune-shaped features along ridgelines, in gullies, or downwind of prominent mid-slope features. You can avoid the problem by choosing terrain where the snow is sheltered or being scoured by the wind.

    (3/12/2023)

    This slab avalanche failed deeper than expected. The slab involved some wind-drifted snow. 

    Photo: Brody Pate

Avalanche Discussion

In a winter characterized by cold temperatures, it's only fitting that the onset of warmer weather has been a slow and incremental process. Yesterday (Thursday), temperatures at mid-elevation weather stations approached 40 degrees Fahrenheit while upper elevations tickled freezing. Building clouds in the afternoon stunted this warming, and the resulting Wet Loose activity was modest. Today looks a couple degrees warmer across the board, with mostly clear skies. If the forecast verifies, anticipate similar activity as yesterday's melt-feeze crust breaks down on solar aspects and dry snow transitions to moist elsewhere.  

Yesterday, BNSF snow safety reported a natural, hard slab avalanche that failed on a buried weak layer during the last week. Continued–albeit few–natural and human-triggered avalanches are keeping this problem on the list. It is most evident in the Flathead Range, southern Glacier National Park, and the Whitefish Range north of WMR.

The southern end of the advisory area in the Swan Range was favored by snowfall earlier this week. In this area, you can anticipate any Wet Loose slides to entrain more snow and grow larger. In upper-elevation, leeward terrain, you can probably still find stubborn drifts of snow capable of producing an avalanche large enough to bury you.

FOFAC Event: March 30th, 2023– Whether you're chasing tan lines, big lines, or both, you'll learn something valuable from FAC Lead Forecaster Mark Dundas about spring avalanche problems, how they differ from winter problems, and how to manage them. We will also discuss current conditions and concerns (or lack thereof!) with our spring snowpack. Enjoy a cold brew from Bias Brewing and a scoop from Sweet Peaks Ice Cream.

The event is free and open to everyone. Begins at 6 pm.

Regions covered